My own shameful lapse happened when our three children were small, the youngest of an age still measured in weeks, but I remember it well enough: after an exhausting and largely unsuccessful trip to the market, my wife is ready to give up, but I am determined to visit the fish shop.

"I'm taking these two to the playground," she says. "Meet us there." She leaves me at the back of the queue with the pram.

The pram takes up a lot of room in the queue, so I push it to one side, out of the way of the men hauling boxes of fish across the slippery floor, but close enough where I can keep an eye while I wait.

I want to be the sort of person who has an easy rapport with fishmongers, but in reality I am the sort of person fishmongers sell unwanted fish to. I'm both highly suggestible and eager to give some impression of expertise. I haven't slept for a month, and I don't know what I want.

When I walk out of the shop with two big bags, I am worried about how I will explain my purchases to my wife. I am specifically wondering how to answer the question: "Why did you buy two-dozen goose barnacles?" I can't say, "Because I wanted the man to think I knew what they were."

To my surprise this is not the first question my wife asks me when I show up at the playground. The first question she asks is: "Where is the baby?" For a brief second I have no idea what she's talking about. What baby? Then I drop my barnacles and run, as fast as I can, all the way back to the fish shop.

By the time I got there the queue was all new people, and I realised they must have all thought someone else in the shop responsible for the pram in the window. My only worry was how I, red-faced and panting, was going to look running in there and snatching a baby. I didn't wait around to find out what anybody thought.

Having three children is a logistical nightmare. It's easy to lose track of one, especially when you try to divide the labours of parenting. My only advice is: do a headcount every hour or so, and always check the top of your car before you set off.